Signaling system



UCL 20, 1942- w. H. T. HOLDEN 2,299,479

SIGNALING SYSTEM File'd April 26, 1941 '7 Sheets-Sheet 1 W H. 7. HOLDEN 'Arrow/EK MOctyI 20, 1942. w. H. T; HOLDEN SIGNALING `SYSTEM y Filed April 26, 1941 7 Sheets-Sheet 2 maw n om SQ /Nl/wrop W H T HOLDEN www f Mmm/Ey .HT- www oct. 2o, 1942. w, H; T. HQLDEN I 2,299,479-

SIGNALING SYSTEM A TTQRNEV OCL 20, 1942 A w. H. T. HOLDEN 2,299,479

SIGNALING SYSTEM 7 Sheets-Sheet 4 all SAQ v .Si

QQYEL W H. 7. HOLDEN ATTORNEY Oct. 20, 194.2. w. H. T. HOLDEN 2,299,479

` `SIGNALING SYSTEM v Filed April 26, 1941 '7 Sheets-Sheet 5 /e PHASE /MPuLsE SUPPLY idf' 544 527 SENDER 2 By W Hf I HOL/25N Oct.' 20, 1942. w. H. T. HOLDEN 2,299,479

S IGNALING SYSTEM Filed April 26, 1941 '7 Sheets-Sheet 6 iq e; @Ag

/NVE/vro@ W H. 7.' HOLDEN I A TTORNEV Oct. 20, 1942.,

W. H. T. HOLDEN 2,299,479

SIGNALING SYSTEM Filed April 26, 1941 '7 Sheets-Sheet 7 W H. 7. HOLDENA f LW/www Patented Oct. 20, 1942 SIGNALING SYSTEM William H. T. Holden, Woodside, N. Y., assignor to Bell Telephone Laboratories, Incorporated,

New York, N. Y.,

a corporation of New York Application April 26, 1941, Serial No. 390,457

Claims.

This invention relates to electric signaling and particularly when used in automatic telephone or other communication systems.

The objects of the invention are to simplify the sending of signal information from one part of a signal system to another; to eliminate much of the connecting equipment heretofore used for establishing signaling connections; to utilize the same transmitting conductors for sending a plurality of sets of signals simultaneously; to ini crease the speed of sending signal information; and in other respects to improve signaling and telephone systems.

It has been the practice heretofore in automatic telephone systems to provide connectors for establishing individual connections between the mechanisms of one group, such as senders, and the mechanisms of a second group, such as switch controlling markers. By providing these connecting devices it is possible to establish a plurality of electrically separate simultaneous connections between a number of senders and a corresponding number of markers. These connectors, however, are expensive since they involve a large amount of equipment, particularly if the sender and marker groups are large. If multicontact relays are employed for establishing the connections, it is usually necessary to provide a relay for each sender in group and one for each marker in the marker group. Similar connecting devices are also required in other parts of an automatic telephone system. For example, in a system of the crossbar type these connectors are used to establish controlling circuit connections between the switch frames and the common markers.

In accordance with the present invention substantial savings and other advantages may be realized over these prior systems by eliminating to a large extent the connecting equipment between the different controlling mechanisms and by providing permanent signal transmitting connections between these mechanisms. More specifically, the foregoing objects of the invention are realized by means of a signal system in which the individual mechanisms of a group, such as a sender group in an automatic telephone system, are connected permanently to all of the individual controlling mechanisms of a second group, such as the group of switch controlling markers, and in which the signal information is transmitted from the senders to the markers by the impulses of a group which vary in phase or otherwise and which are transmitted during each of a succession of cyclically recurring impulse periods, each period in the cycle representing a particular one of the markers and the particular sender from which it is receiving the signal information. By means of a relatively simple selecting circuit arrangement each calling sender the sender sender.

appropriates for its use the rst idle one of the markers and excludes other senders from the use of the seized marker. During each of the successive impulse periods a plurality of iinpulses of different phases are produced, and the particular marker which is characterized by such impulse period is enabled to the exclusion of the remaining markers. According to the information registered in the sender that has seized the enabled marker, impulses of the appropriate phase are transmitted from the sender over the common signaling conductors to the enabled marker where they serve to register the information corresponding to that first registered in the Since the other markers are disabled during this particular impulse period, they are not affected. During the remaining impulse periods of the cycle, representing the corresponding markers, phase impulses are transmitted from the senders over the common signaling conductors to the corresponding markers which have been seized by these senders, only one marker being enabled in each impulse period to permit the signal information to pass to such marker to the eXclusio-n of all others. Therefore, several signaling channels may exist concurrently between senders and markers, and the information pertaining to each sender and its associated marker is transmitted over the common connecting conductors or medium without interference with other channels.

The foregoing and other features of the invention will be discussed more fully in detail in the following specification.

In the drawings accompanying the specification:

Figs. l to 7, when arranged as illustrated in Fig. 8, disclose an automatic telephone system incorporating the features of the invention.

1 illustrates in diagrammatic manner the line switch and certain of the selector switches of an automatic telephone exchange and also a sender link or sender selector switch for associating the calling lines with idle common register senders;

Figs. 2 and 3 show a portion of one of the common register senders;

Fig. 4 is a diagrammatic illustration of a second one of the register senders;

Fig. 5 illustrates a third one of the register senders'and also shows a counting mechanism for producing cyclically the periods during which the successive markers are in a receptive condition;

Fig. 6 shows a portion of one of the common switch controlling markers; and

Fig. '7 illustrates diagrammatically two more of the common markers and also shows a testing mechanism for determining the condition of the common transmitting medium between the senders and the markers.

The present invention in its broadest aspects relates to the transfer of signal infomation over a common medium between sending devices of one group and receiving devices of a second group, and it should be understood that said invention is not limited in its application to telephone systems or to systems oi any other particular type. It is, however, especially useful in automatic telephone systems where registered designations and other kinds of information must be transferred from one part of the system to another during the controlling operations incident to the establishment of the desired connections. Therefore, the invention has been illustrated herein when applied to the common register senders and the common switch controlling markers of an automatic telep-hone exchange system of the Wellknown crossbar type. For a better understandingr of the various operations involved in these systems and of the details of the equipment used, reference may be had to numerous patents, including the patents to W. W. Carpenter, 2,093,117 of September 14, 1937, and 2,235,803 of March 18, 1941.

Referring to the drawings, the subscribers lines appear in the crossbar switches lili) and through these switches have access over trunks Hill, |02 to the district selector switches m3. The district selectors have access over trunks |04 to office selector switches Il, and these in turn have access to the groups of outgoing trunks |516. The calling lines also have access through the sender selector svvitches lill' to the common register senders which receive and store the telephone designations.

Three of these senders, 263, |69 and 50S, are illustrated in the drawings, and as many more could be provided as are needed to handle the traino through the cnice.. The senders are seized at random in response to calling lines and receive and register the designations transmitted from the calling substaticns. Thereafter the senders transfer these registered designations to the common switch controlling markers, which in turn make use of the designations received from the senders to control the selective operation oi the automatic switches. Three of the common switch controlling markers, markers S, Tll and lill, are shown in the drawings and as many more would be provided as are needed.

In the systems oi the prior art, as hereinbefore mentioned, connecting devices are required for selectively connecting a calling sender with an idle one of the common markers. If, for example, four or five senders are in use concurrently, each serving a calling line, these connecting devices serve to establish individual and separate connections between each of the calling senders and each of the associated markers. In this way, the designation information may be transmitted at the same time from as many of the senders as there are markers, and no interference results because t-he connections are separate from each other. In the present system, however, these intermediate connecting devices between the senders and the markers have been eliminated, and a common transmitting medium comprising the conductors 2MB is connected permanently and in multiple between all of the senders d, 4530, S, etc., and all of the common markers 660, 100, 'l I l), etc. As will be explained hereinafter, the signal information for a plurality of senders, which may be taken for concurrent use, is transmitted over the common medium 2 I3 to the respective markers without mutual interference by the use of impulse signals occurring in different time periods and in different phases in each of said periods.

Each of the register senders includes registers for the office and numerical portions of the telephone designations, means for transmitting the office registration over the common medium to the associated marker, the usual means for transmitting the numerical designation to distant senders, together with controlling relays and circuits. Two office code registers 29| and 292 have been shown in full in the sender 2&6, the assumption being that the oiiice part of the designation consists of two letters or other characters. Two groups of transmitting tubes 2&33 and 295|, associated with the registers 26| and 232, respectively, serve to transmit the oice registration over the conductors of the common medium 2 0 to the associated marker. The sender 25|) is also provided with a marker selector or allotter 300 comprising space discharge tubes 30|, 362, 333, there being one of these tubes for each of the markers to which the sender has access. Furthermore, the sender Z is equipped with a plurality of groups of discharge tubes 205, 206, 3M, each group consisting of ten tubes, there being as many of these groups as there are markers to which the sender has access. The purpose of the tubes 2%, 2%, 3M is to select from the cyclically recurring periods the particular period representing the marker which has been seized by the sender and to deliver to the transmitting tubes 2&3 and 2M during the selected period the phase impulses which serve to characterize the values of the code digits registered on the registers l and 2232 of the sender. To this end one of the groups 2635, 2%, 3M, namely, the group characterizing the seized marker, is rendered effective by the particular one of the tubes 3M which operates to cause the seizure of said marker and the remaining groups of tubes remain ineilective.

In like manner each of the remaining senders is provided with a marker-allotter, with transmitting tubes, and with a plurality of groups of tubes corresponding to the groups 235, 286, 304, for selecting the proper periods for the signal transmission. The several allotters are so related to each other that each calling sender selects and seizes the rst available idle marker, and each busy marker is rendered unselectable to all other senders. Thus, if a plurality of senders are concurrently associated with a corresponding number of markers, the transmitting tubes of these senders are rendered effective during the respective transmitting periods corresponding to the seized markers. In other words, one of the calling senders will transmit its signal information over the common medium to the associated marker during the particular one of the sending periods which characterizes said associated marker; the next sender will transmit its information during the particular period characterizing the marker with which it is associated; and the same is true of each of the remaining senders which may concurrently use the transmitting medium.

The marker Geil (and the same is true of each of the other markers) is equipped with two relay registersV 66| and 662 for registering the oice code digits and with corresponding sets of discharge tubes 603 and BM which receive from the sender the impulses representing these digits and cause the operation ci the corresponding relays of said registers. The marker is also provided `mine and control the selective with two sets of receiving tubes 605 and 606, one ,for each of the oi`n`ce code digits, which receive the digitimpulses incoming over the conductors 201 and 208 from the sender, These receiving tubes 605 and 600 are rendered eiective only during the impulse period which characterizes the marker 600 and are ineffective to receive impulse signals during the transmitting periods characterizing other markers. The effectiveness of these receiving tubes 605 and 606 is controlled by the timing mechanism 50| which cyclically produces the impulse periods characterizing the different markers.

The marker is also provided with the necessary routing relays and other controlling `circuits and devices whereby the office designation registered on the registers 60| and 602 is utilized to deteroperation of the switches |03 and |05. These controlling means are illustrated by the diagram 601 and have not been shown in detail since they are well understood in the art.

The phase impulses by which the signal information is transferred from the senders to the markersare produced by a common impulse generator 502. The energy for this generator is supplied from an alternating current source 503, and the generator in response to each cycle of the source 503 produces impulses of in each one of the output circuits 504. There are twelve of these phase circuits, and the rst ten of them are used for sending the signal informa,- tion between the senders and the markers. The eleventh phase is used for the marker testing mechanism shown in Fig. '.7, and the twelfth phase is used to operate the period measuring mechanism 50|. The rst ten phase circuits 505 are connected over corresponding conductors 506 to the primary windings of the ten transformers 2| I, 2|2, 2|3, associated with the anodes of the ten tubes of the group 205. More speciiically the conductor 501, to which impulses of phase No. are delivered by the generator 502, is connected to the transformer 2|| associated with the No. 0 tube 2|4. Likewise the remaining conductors of the group 5.06, including conductor 509 to which impulses of phase No. 9 are delivered, are connected to the transformers associated with the remaining tubes of the group 205, Furthermore, the ten impulse conductors 505 are multipled and connected `to the input transformers associated with the respective tubes of each of the remaining groups 205, 304, etc. Thus the signal impulses of the ten different phases are applied once per cycle of the generator 502 to the anodes of the corresponding tubes of the groups 205, 206, 304, etc. Since only one of these groups is eiective in a particular sender, such as sender 200, only the tubes of the effective group discharge and pass impulses to the transmitting tubes 203 and 204. Furthermore, only one tube in each of the groups 203 and 204 is rendered effective by the corresponding registers 20| and 202. an impulse of the phase corresponding to the operated relay of register 20| is transmitted through the corresponding tube 203 to the common conductor 201 and thence to the receiving tubes 605 of all markers. Likewise a single impulse corre-1 sponding to the operated relay of the second register 202 is transmitted through the corresponding tube 204 and over conductor 208 to the receiving tubes B06 of all markers.

The discharge tubes 203, 204, 205, 200, 304, 300, 603, 504, 605, 606 and the tubes 10| and 102 may a different phase Hence i nected overconductors 3| 6, 3

b e of any suitable type such as those commonly 3 known in the art as gas-filled tubes. The tubes of the group 5| may also be of 'the gas-'lilled type, but these are preferably equipped with heated cathodes. i y The impulse generator 502 may be of any suitable type whereby brief impulses of positive polarity of twelve successive phases are generated during each cycle of the source 503. Generators of this type are illustrated in the application of W. H. T. Holden, Serial No. 361,536, led October 17, 1940,- and the patents to W. H. T. Holden, No. 2,252,766 of August 19, 1941, and No. 2,285,815 of June 9, 1942.

The operation of the transmitting system will now be described in detail. For this purpose it may be assumed that a call is made by the subscriber 0f line ||0. A call by this subscriber causes the operation of the line switch |00 to extend the line over an idle junctor |0| to the district selector |03 and also through the sender selector |01 to an idle one of the register senders such as the sender 200. Upon the seizure of the sender the start relay 305 operates and closes a discharge circuit as follows for the tube 30E: negative pole of battery 301, contact of relay 305, resistor 308, control gap electrodes of the tube 300, resistor 309 to the positive pole of battery 3|0. The tube 300 ionizes its control gap, and current flows in the main discharge circuitof said tube, including the slow-release relay 3|| and the alternating current source 3|2. The relay 3|| operates and retains its armature during the time the voltage from the alternating current source 3|2 is passing through zero value at each alternation. Relay 3| connects the positive pole of battery 3|3 through resistor 3M to the main anodes of all of the tubes 30|, 302 and 303. The operation of relay 305 also connects the negative pole of battery 301 through resistor 3|5 to the start cathodes of all of the tubes 30|, 302 and 303. The start anodes of these tubes are con- |1, 3| 8 through the potentiometers 40|, ,402, 403, respectively, to ground. These potentiometers are also connected to respective ones of the phase impulse conductors 505. As illustrated, the potentiometers are connected respectively to the No. 0, No. 1 and No. 9 phase impulse. conductors 501, 508, 509; although they may be connected as desired to any corresponding number of these conduc-4 tors. The purpose of these potentiometers 40|, 402, 403, etc., is to deliver potential impulses at spaced intervals to the starting anodes of the allotter tubes 300. .i

Assume that the No. 0 marker 630 is idle at the time the sender 200 is seized and the start relay 305 operated and that the impulse generator 502 has just passed the phase corresponding to lthe last idle marker in the group following marker 000 at the time relay 305 is operated to condition the allotter tubes 303. When, therefore, the generator 502 commences its next cycle and an impulse of positive polarity is generated in the No. O phase conductor 501, this impulse is applied through the potentiometer 40| over conductor 3|6 to the starting anode 3i9 of tube 30|. Since negative potential is applied to the starting cathode 320 of this tube, the voltage across the control gap 3|9320 is sulicient to ionize the tube. The momentary flow of current through the resistance 3|5 when the control gap ionizes alters the potential of the starting cathodes of the remaining tubes 302 and 303 of the sender 200 to discourage the ionization of a second one of these. `tubes when the startingl anode thereof is raised to a positive potential in response to the next phase' impulse. The ionization of the contro-l gap'of the tube 30| causes transfer of the ionization to the main gap, and current now flows from the positive pole of battery 3|3, contact of relay 3| I?, resistance 3|4, anode 32|, main cathode 322, conductor 323, inductor 454, resistor 495 to the negative pole of battery 495. Since the inductor 404 is common to the allotter tubes in all. senders corresponding to tube 39|, the voltage dropv produced by the inductance of this element alter the potential on the cathodes of these tubes to prevent another one of them from discharging and seizing the same marker. As soon as the current flow in the main discharge circuit of tube reaches a steady state the voltage drop across the common resistor 505 serves the same purpose of preventing another one of the senders, that may be seeking a marker while sender 200 is in use, from causing the discharge of its allotter tube corresponding to the tube 39 i. Thus the' tube 30| of the calling sender 290, which identies the idle marker |555, has been operated to the exclusion of the remaining tubes of the allotter 300 and in its operated condition guards against the subsequent operation of the corresponding tube in any other one of the senders.

The operation of tube i eiiects the seizure of the marker G50 by energizing the group of tubes 205 representing said marker to the exclusion of the remaining tube groups 255, 394, etc., representing other markers. The flow of current in the main dis-charge circuit of the tube 35i raises the collector electrode 324 to a positive potential With respect to the cathode 322. This positive potential is transmitted over conductor 325 through resistors 2l5, 2|1, 2i0 to the starting anodes of tubes 214, 2l5, 219 of the group 295. Since the cathodes of these tubes are at negative potential the starting gaps of all tubes ionize. For example, the circuit for ionizing the starting gap of tube 214 may be traced from conductor 325, resistor 2 l0, starting anode 229, cathode 22|, transformer winding 222 to the negative pole of battery 225. The other tubes of the group 295 are ionized in similar circuits.

The sender 250 having been seized and connected to the calling subscribers line |10, the subscriber now proceeds to operate his dial to send the Wanted designation, including the office code digits and the usual numerical digits, into the sender. The two code digits cause the operation of the registers 20| and 202 in the wellknown manner, and one of the relays in each of these registers is energized to register the value of the digits. Assume that the ofiice code is represented by the digits 1-9, in which case the relay 224 of register 20| and relay 225 of register 202 are operated and all of the other relays of these registersl` remain deenergized. The operation of register relay 224 completes a circuit from the positive pole of battery 235, contact of relay 224, resistor 244, starting anode 230 of transmitting tube 233, cathode 231, conductor 201 through the primary winding of transformer 609 to the negative pole of battery 509. The voltage applied to the control gap of tube 233 in this circuit causes the tube to ionize preparatory to the transmission of a signal impulse from the sender to the marker representing the oiiice code digit 1. Similarly, the operation of register relay 225 closes a circuit from the positive pole of battery 235, contacts of relay 225, resistor 245, starting anode 238 of tube 239, cathode 240, conductor 208, the primary winding of transformer @I0 to the negative pole of battery 6H. The control gap of tube 239 ionizes in this circuit preparatory to the transmission of the signal impulse representing the code digit No. 9.

It will also be assumed that the subscriber of another line, such as line |20, initiates a call at about this time. Line |20 is extended over the line switch |00 to an idle junctor |02 and through the sender selector switch |01 to the next idle sender in the group, such as sender 495. The seizure of sender 400 causes the closure of the start circuit and the operation of the allotter tube, corresponding to tube 352 of sender 200, assuming the next marker to be idle. The operation of the tube in sender 450 representing the idle marker 100 serves to condition the group of tubes in sender 400 corresponding to the group 255 shown in full in the sender 200. In other Words the initiation of a second call concurrently with the first one causes the selection of the second idle sender 459, Which in turn seizes the next idle marker 100 and prepares the impulse transmitting tubes in the sender for sending its information during the transmission period of the seized marker. In like manner other concurrent calls result in the seizure of idle senders and the connection of these senders to respective idle markers. Assuming, however, that only the tWo senders 200 and 400 are in concurrent use at this time, an explanation will now be given of the manner in which the transmission periods are produced cyclically and of the manner in which these senders transmit their information over the common medium to the associated markers during the transmission periods assigned to these particular markers.

As hereinbefore mentioned, the transmission periods are produced by the time measuring mechanism 50|, which consists of a plurality of hot cathode gas-iilled tubes 5|0, 5H, 5|2, etc. The cathodes of these tubes are heated by i'llaments energized through the transformer 524 by a suitable source of alternating current 525. The tubes 5|8, 5| 552, which correspond to the respective transmission periods, are ionized and deionized in succession by impulses delivered from the generator 552 in the No. 12 phase position thereof. That is, once per cycle of the generator 552 an impulse is delivered over conductor 5|3 to the mechanism 55| to cause the ionization of the next succeeding tube and the deionization of the tube already in an ionized condition. The No. l2 phase position Yis chosen so that the transmitting tubes of the senders may be conditioned and ready to receive the designation impulses when, subsequently, the generator 592 passes through phase positions No. 0 to No. 9. In order to describe the details of the mechanism 50| it may be assumed that tube 5|2 is in an ionized condition. Therefore, current iiows from the positive pole of battery 5M from the anode 5|8 to the cathode 5&9 of tube 5|2 through the resistor 5i5 te ground. This current flow raises the cathode to a positive potential with respect to ground, and charging current flows through the condenser 5&5 and resistor 5|1 to ground. The condenser 515 assumes a charged condition in this circuit. The positive potential of the cathode 519 is applied over conductor 520 through the potentiometer resistance 52| to the grid of tube 510, which is the next tube in the series. rI'he resultant of this positive potential applied through the potentiometer resistance from the cathode 529 and the negative potential applied from the biasing battery 523 through resistor 522 renders the grid of tube I 0 less negative than normal but not sufficiently positive to allow discharge to occur. The positive potential of the cathode 5|9 is also applied through the choke coil 526 over conductor 521 through the windings of the associated transformers to the anodes of the ten tubes of the group 304 in the sender 200 and likewise to the anodes of the corresponding groups of tubes in all of the other senders. Since, however, the marker 1|0 to which the group of tubes 304 relates is not in use at this time, the application of this potential to the anodes of these tubes is without effect.

When the generator 502 completes its next cycle and reaches phase No. 12, an impulse is applied over conductor 5|3 tothe potentiometer resistance 528 and thence through ccndensers 529, 530 and 53| to the grids of the tubes 5|0, 5| 5I2, respectively. The normal negative potential of the grid of tube 5| applied thereto by the battery 523, is suiiiciently high so that the positive impulse applied to the grid through condenser 530 does not cause the tube to discharge. The grid of tube 5|0, however, is more positive than its normal biasing potential by reason of the positive potential of the cathode 5I9 of the operated tube 5|2. Therefore, when the positive impulse is applied through the condenser 529, the grid 5|0 is made sufiiciently positive to cause this tube to discharge. Current now iiows from battery 5| 4 from the anode 532, cathode 533, resistor 5H to ground. The positive potential of `the cathode 533 is now applied over conductor 534 to the right-hand terminal of the charged condenser SI5. This raises the potential of the other terminal of condenser 5I6 and cathode 5|9 to a value suiiicient to extinguish the discharge in the tube 5|2. Thus the impulse applied to the conductor 5|3 ionizes the next tube 5|0 and extinguishes the preceding tube SI2. As soon as the tube 5i2 is extinguished, the condenser 5| 6 dissipates its charge through resistances 5| 5 and 5| 1. The positive potential of the cathode 533 causes the charging of condenser 535 through the resistor 536. Also the positive potential of cathode 533 is applied through the potentiometer resistor 538 to render the cathode of the next tube 5I I more positive than normal, thus conditioning the tube 5|I for operation when the next impulse is received. As soon after the tube 5|0 discharges as the surge is absorbed by the choke coil 539 and condenser 540, the full positive potential of the cathode 533 is applied over conductor 54| through the windings of transformers 2|I, 2| 2, 2I3 to the anodes of all ten tubes in the group 205 and similarly to the anodes of the tubes of the corresponding group in each of the other senders.

ince the control gaps of the ten tubes 205 are ionized as above explained, current now flows through the main discharge gaps of these tubes. For example, the circuit for the ow of current in the main discharge gap of tube 2|4 may be traced from conductor 54|, to which positive potential is applied by the measuring mechanism 50| during this period, Winding of transformer 2||, main anode 225, cathode 22|, transformer winding 222 to the negative pole of battery 223. Similar circuits are traceable from the remaining tubes in the group 205. During this transmission period, which continues as long as the tube 5|0 of the mechanism 50| is in a conducting condition, and during which period the relays of the `group 205 are conducting, the generator 502 passes through its first ten phases No. 0 to No. 9

and transmits impulses of these phases over the conductors 505 and 506 to the primary windings of the transformers 2| I, 2|2, 2| 3, associated with the anodes of the tubes 205. For instance, in phase No. 0 of the generator 502 an impulse is transmitted over conductor 501 through the pri-` mary winding of transformer 2I| to ground. This impulse is induced in the secondary winding of transformer 2| and produces a corresponding increase in the current iiow through the transformer winding 222. This increased flow of current produces an induced impulse in the transformer winding 221 which appears as a positive potential impulse on the anodes 228 and 229 of the No. 0 transmitting tubes 230 and 23|, respectively. Similarly, in phase No. 1 of the generator 502 an impulse is transmitted over conductor 500 through the primary winding of transformer 2|2, and a corresponding impulse is produced in the transformer winding 232 and appears as a potential impulse on the anodes of the two No. 1 transmitting tubes 233 and 234. Likewise, each of the remaining eight phase impulses are sent in succession to the remaining tubes of the group 205 and are reproduced as impulses on anodes of the corresponding transmitting tubes of the groups 203 and 204. Although these impulses are applied to the anodes of all tubes in the groups 203 and 204, discharge occurs only in the main gaps of tubes 233 and 230, these being the only tubes that have their control gaps ionized in response to the operation of the register relays 224 and 225. Therefore, current iiows from the anode 24| of the 'ionized tube 233 to cathode 231 thence over conductor 201 through the primary winding of the transformer 600 to the negative pole of battery 609. Likewise current flows from anode 242 to cathode 24,0 thence over conductor 208 through the primary winding of transformer 6| 0 to the negative pole of battery 6| I. Similarly these signal impulses, which are transmitted from the sender 200 over the conductors 201 and 208 to the marker 600 in phase positions No. 1 and No. 9, are also transmitted to each of the remaining markers 100, 1|0, etc. As above mentioned, however, only the tubes 605 and 606 of marker 600 are in a transmitting condition during this transmission period. The ionization of these tubes during this period is effected over the circuits from conductor 54 I, on which a positive potential is maintained by tube 5|0, resistors 030 and 53|, windings of transformers 6|2 and 620, tubes 605 and 000, to ground, respectively, through the windings of transformers 008 and 5| 0. Consequently the signal impulses transmitted over the conductors 201 and 208 are conducted through the tubes 505 and 606 but are not conducted through the corresponding tubes in any other marker.

When tube 505 transmits f the incoming impulses of phase No. 1, an impulse appears in the secondary winding of transformer 0|2 and is applied through resistor 6| 3 to the starting anodes of all ten of the receiving tubes 603 in the marker. At the same instant, namely, in phase No. 1 of the generator 502, an impulse is supplied over conductor 508 through the windings of transformer 6|4 to the starting cathode of tube SI5. The voltage thus produced by the simultaneous applications of these impulse potentials, which are of opposite polarity, to the starting electrodes of the single tube SI5 causes the ionization of the control gap, whereupon a discharge circuit for the main gap of the tube is closed from the generator supply lead 542, which has positive potential thereon at this time, through the winding of slow-release relay U, anode Gil of tube M5, cathode titi to the negative pole of battery SH2. Relay tit operates in this circuit to register the code digit l in the marker. In like manner the transmission of phase impulse No. 9 through the ionized tubes 626 causes an impulse in thesecondary winding of transformer 62), which impulse is applied through the resistor 62| to the starting anodes of all tubes in the group GM. At the same instant, namely in phase No. 9, an impulse is applied from the generator 5M over conductor ccs through the windings of transformer G22 to the starting cathode of tube 623. The simultaneous potentials on the electrodes of tube i323 being of opposite polarity by reason of the direction of the transformer windings, the tube icnizes its starting gap, and current flows from the generator supply lead 542 through the winding ci slow-release relay `524, anode 25 of tube S23, cathode 626 to the negative pole of battery 527i. Relay G24 operates to register the code digit 9. Although phase impulses of the ten different phases are applied to the starting cathodes of all `tubes in the groups 623 and Bild during this transmission period, only the two tubes @i5 and .B23 operate because these are the only tubes having simultaneous impulses applied to their starting anodes from the common transmitting conductors 221 and 298. Therefore. only the registers 'BIB and 624 operate as explained. operation of these register relays Sit and G22 causes the selection and operation of the proper routing relay in the controlling and routing -l mechanism 621, wherefrom the routing of the call and the operation of the selector switches is determined.

At the end of the transmission period just described, during which the registration was transmitted from the sender 222 to the associated marker Bilt), the generator 5!2 enters phase No. 11, and another impulse is transmitted over conductor 5i3 through the condensers 529, i532 and 53| to the grids of the tubes 5H), 5H, 512. Tube 512 is unaiected by this impulse, but tube E! l, which has been conditioned by the operated tube EID, discharges, and current ows through the resistance 536 to ground. In the manner already described the discharge of tube 5H exr tinguishes the preceding tube 5m and conditions the succeeding tube 552 for operation at the end of the next transmission period. The extinguishment of the tube 5M) removes the positive potential from the conductor 5M and also from the anodes of the tubes of the group 26H5 in the sender 2M! and from the corresponding group in each of the remaining senders. Consequently the tubes 2555 and the corresponding tubes in other senders cease to conduct current through their main discharge gaps.

AThe flow of current in the resistance when the tube 5H discharges as above explained causes the application of a positive potential through the choke coil be2 over conductor 5M through the associated transformer windings to the anodes of the ten tubes `of the next group 226 of the sender 229 and of the corresponding group in each of the `remaining senders. The application of this potential to the anodes ci the tubes 225 is without effect since the sender 2% at this time is associated with marker and the `tubes 295 lare inactive. In the sender lii, however, which is associated with marker 'X20 at this time, the ten relays corresponding to relays 265 have their control gaps ionized, and the application of the positive potential over conductor 545 to the anodes ci these tubes in the sender causes them to discharge their main gaps preparatory to the transmission of signal impulses through the tubes corresponding to the transmitting tubes 2F13 and 204 and thence over the common transmission conductors 2&1 and 298 to the marker WQ. Thus as the impulse generator 522 passes through its phases No. 0 to No. 9 for the next period impulses of the particular phases characterizing the operated register relays in the sender lim] are transmitted over the conductors 2M and 268 and are recorded only on the registers of the marker 'wil with which sender [im] is associated.

At the end of this second transmission period the time counting tube SI2 discharges and extinguishes the preceding tube 5H and prepares the sender 520 for transmitting its record, in case it is engaged at this time, to the marker with which it is associated. In like manner the transmission periods follow in succession under the control of the counting mechanism '585, and the records of all engaged senders are transmitted during the appropriate periods over the common conducting medium to the associated markers.

After all controlling functions have been completed by the marker i308, the sender relay 305 may be released to open the ionizing circuit for the control gap of the tube 325. On the next opposing cycle of the source 3HE the main gap of the tube 335 quenches, and relay 3H releases to open the discharge circuit of the allotter tube dei. The tube 32! quenches and remo-ves potential from the starting anodes of the tubes 22'55 permitting these tubes to quench their control gaps. The quenching of the tube 3M also restores the potential of the main cathode of the corresponding tube in each of the remaining senders so that the marker GS@ will appear idle to these other senders. Also the sender 202 is released after it completes all the functions i necessary in connection with the extension of the calling line tc its destination and is free for selection by other calling subscribers lines..

Each time the generator 592 passes through phase No, 10 a test is made to determine the continuity and operating condition of the common transmitting conductors 29? and 288 extending from the senders to the markers. This test is performed by the testing and alarm mechanism shown in Fig. 7. As the generator 592 enters phase No, 10 an impulse is transmitted over impulse lead 525 through the discharge tubes 545 and 5t? thence over conductors 5138 and 549 to join conductors 2&1 and 283, respectively, at a point near the first sender Zli, and from thence the circuits continue over conduc tors Zil and 203 to the starting anodes. of the tubes IGI and 152, respectively. At the same instant an impulse of phase No. 1D is transmitted over conductor 550 through the winding of transformer to ground. The impulse produced in the secondary winding of the transformer TG5 is applied to the starting cathodes of the tubes 'itil and e2 and is opposite in polarity to the impulses applied to the starting anodes. Therefore these tubes icnize their control gaps, and current flows from the generator supply lead 52,2 through the windings of slow-release relays W3 and ltd, main anodes of the tubes 'mi and 'm2, main cathodes of these tubes to the negative pole of battery 735. These impulses recurring in the conductors 201 and 208 once per cycle of the generator 2 are sufficient to maintain the relays 1&3 and 'E04 continuously operated to hold open the alarm circuits 101. However, should a failure occur in one of the conductors 281, 2te, the ionizing impulses cease to appear, and the corresponding relays 103, 104 release to close the alarm circuit.

What is claimed is:

1. In combination, a group of sending devices, a group of receiving devices, means for registering information in said sending devices, a common signaling medium permanently connecting each of said sending devices with all of said receiving devices, means for seizing said sending devices for use, means for causing each sending device taken in use to seize an idle one of said receiving devices, means for producing a group of impulses in each one of a succession of time periods, said group comprising impulses of a plurality of phases, said impulse periods representing, respectively, said receiving devices, means for sending over said signaling medium from the sending devices to the receiving devices impulses of said plurality of phases in each of the time periods representing a seized receiving device for the purpose of transferring over said medium the information registered in all sending devices in use, means in each receiving device for selecting the phase impulses in the period representing such receiving device, and means in each receiving device responsive to the phase impulses selected for` registering the information transferred from the sending device that seized said receiving device.

2. In combination, a group of sending devices, a group of receiving devices, means for registering information in said sending devices, a common signal transmitting conductor joining all of said sending devices in a continuous conducting path with al1 of said receiving devices, means for seizing for concurrent use variable numbers of said sending devices, means for causing each sending device taken in use to seize the next idle one of said receiving devices, means for producing a group of impulses in each one of a succession of time periods, each group comprising impulses of a plurality of phases, said impulse periods characterizing, respectively, said receiving devices, means controlled by said impulse producing means for enabling each one of the seized receiving devices during the corresponding impulse period, means for sending over said common conductor from the sending devices tc all of the receiving devices impulses of said plurality of phases in each of the time periods characterizing a seized receiving device for transferring the information registered in all sending devices in use, means in each receiving device responsive to said phase impulses during each period said receiving device is enabled, and means in each receiving device responsive to the phase impulses received for registering the information transferred from the corresponding sending device.

3. In combination, a group of sending devices, a group of receiving devices, means for registering information in said sending devices, a signaling conductor permanently and continuously connected between all of said sending devices and all of said receiving devices, means for seizing for concurrent use a variable number of said sending devices, means for causing each sending device taken in use to appropriate for use an idle one of said receiving devices, a source for producing a group of impulses in each one of a plurality of successive time periods, said group comprising impulses of a plurality of phases, means for rendering the appropriated receiving devices effective, respectively, during successive impulse periods and for repeating said periods cyclically, means for sending over said signaling conductor from each sending device in use an impulse of the phase characterizing the information registered in said sending device in the time period corresponding to the appropriated receiving device, and means in each receiving device responsive to the phase impulses received during the period such device is effective for registering the information transferred from the associated sending device.

4. The combination in a telephone system of a group of senders, a group of markers, means for registering telephone information in said senders, a common signaling conductor permanently connecting all of said senders with all of said markers, means for seizing a number of said senders for concurrent use, means for causing each sender to appropriate for use an idle one of said markers, a source of alternating current, means for generating a group of impulses in each of a plurality of successive time periods, each period corresponding to a cycle of said source and characterizing a particular one of said markers, said group comprising impulses of a plurality of phases, means for sending over said signaling conductor from each sender in use an impulse of any one of said phases in each of the time periods characterizing an appropriated marker, said phase impulses representing the information registered in said senders, means controlled by said impulse generating means for rendering each appropriated marker responsive to the phase impulses transmitted during each of the successive periods characterizing said marker to register therein the information transferred from the associated sender, and automatic switches controllable by the information registered in said markers for establishing telephone connections.

5. The combination in a telephone system of a group of senders, a group of markers, means for registering telephone designations in said senders, a common signaling conductor connecting all of said senders in multiple with all of said markers in multiple, means for seizing any one or more of said senders for concurrent use, means for causing each sender taken in use to appropriate an idle one of said markers, a source of alternating current, means for generating a group of impulses of different phases in each of a plurality of successive and cyclically recurring time periods, each period corresponding to a cycle of said source, each period representing one of said markers, means for sending over said signaling conductor from each sender in use to all of said markers an impulse of any one of a plurality of said phases during the impulse period representing the particular marker appropriated by such sender, means controlled by one of the phase impulses produced in each of the successive impulse periods for enabling the corresponding marker to the exclusion of the remaining markers, and means in each marker responsive during each period in which it is enabled for receiving and registering the phase impulses transmitted from the associated sender.

WILLIAM H. T. HOLDEN. 

